You can also determine what the "calibration" is at a lower power. I wont go into it because there are numerous threads that explain it better, but simply put:
xx MOA at 22x or XY MOA at 15x; Many people do also find out what power matches Milradian Marks, thus having a scope marked to to Mil and MOA.
Bullets have well documented performance specifications.
Min Velocity info is available, and describes the performance floor of the bullet... DON'T allow yourself to reference F.P.E. as an accurate descriptor of killing power.. You are smarter than a copy editor, and you understand that you can determine maximum (reliable) effective range by comparing your drop chart to published bullet data....... And, dog-on-it, people like you!